(1) Field of the Invention
The present invention relates to a termite detecting device and a method of detecting termites whereby damage caused by termites entering houses is located and identified.
(2) Description of the Prior Art
Termites exhibit negative phototaxis (or move away from light) so that they nest in unobservable, dark places to lead their lives. Therefore, it is very hard to detect invasions of termites into houses.
Termites are insects that belong to a family of Isoptera. As there are reportedly about 2050 species of termites scattered all over the world, they are known as a common harmful organism which damages buildings in both Occidental and Oriental countries.
For instance, mainly, two species of termites inhabit Japan, namely, `Yamato-Shiroari termites` and `Ie-Shiroari termites`. These are called underground termites, which nest under the ground to eat away wood of houses in dark places to hollow out the inside of wood.
As termites have swarming behavior, a large number of the Yamato-Shiroari termites, for example, forming huge aggregation, happen to swarm from their nest after the emergence in April and May. In most cases, this would be the first notice or finding of the invasion of the termites.
That is, in practice, it is not until a large number of termites in the winged form (winged ants) swarm away in spring from their nest that the habitant notices the existence. Therefore, at the time, damage to the house would be in the advanced stage and it would, in most cases, be too late to deal with the damage.
In order to deal with this, for detecting invasions of termites in the early stage, possible structures to be damaged have been subjected to `cavity sound test`, `detecting test of termites on eating or destructive action sounds`, `visual observation under floors`, or `periodical visual observations of testing wood set in expected invading passages of termites to a building under test`.
Nevertheless, of all the aforementioned early-stage detecting means of termites, `cavity sound test` and `detecting test of termites on eating or destructive action sounds` require skillful staffs to go to the place to be tested so as to examine all the possible parts of the structure of the building. Accordingly, these methods take a great deal of payment and labors. Particularly, in the case of `detecting test of termites on eating or destructive action sounds`, it would be difficult to surely detect the existence of termites when the detection was performed in an inactive period (especially in winter) of the termites or at an inactive time of them.
As depending upon the locations, the most active period and time of termites is typically considered to be from April to October during the time from nightfall to midnight. Other than that period and that time, termites are hard to detect.
In addition, most of the houses based upon the recent architectural techniques have minimal underfloor spaces, so that the underfloor space is hard for an inspector to enter, thus making it extremely difficult to execute `visual check`. Besides, as to bathrooms where termites are most likely to invade for feeding, it is impossible to enter the underfloor space thereof, therefore, the visual check of the bathroom is actually unfeasible.
With respect to the method by `periodical visual observations of testing wood set in expected invading passages of termites to a building under test`, since a professional staff must periodically carry out visual inspections of a considerable number of the testing wood for each house by pulling them out from the earth, this work requires a rather high cost and much labor.
In order to solve the problems stated above, various kinds of proposals have been made other than the aforementioned method disclosed in Japanese Patent Application Laid-Open Sho 63 No. 56240 in which, as stated above, whether or not termites exist in the wood placed in the intruding paths is observed. Another method, as disclosed in Japanese Utility Model Application Laid-Open Hei 1 No. 118677 and Japanese Patent Publication Hei 4 No. 21449, is that, termite-detectors formed of a wooden container with a termite-detecting sample inserted into a hollowed inside thereof are buried in the earth in such positions as to be expected to be invading passages of termites, and the thus accommodated, detecting samples are periodically or irregularly drawn out so as to be visually observed for checking the existence of termites. This method is to take advantage of the taxis for channel of termites which causes termites to be attracted to a clearance formed between the wooden container and the inserted detecting sample.
Another alternative method is disclosed in Japanese Utility Model Laid-Open Sho 61 No. 142586. According to the disclosure, two or more than two termites' favorite wooden pieces are jointed together by a jointing means in a detachable manner so as to form one or more joint portions. The thus formed joint portions are checked on termite-eaten damage, periodically, in order to monitor the activity situation of termites.
A method of inspecting damages by general wood-destroying insects, as is disclosed in Japanese Patent Application Laid-Open Hei 2 No. 251750, is that the inside of a wood under test is inspected from the outside using a supersonic non-destructive tester, etc., to examine whether or not there is any cavity or hollow inside the wood. An alternative method, as is disclosed in Japanese Patent Application Laid-Open Hei 3 No. 102257, is that the sound from the inside of a wood being damaged is observed with an acoustic emission sensor (which will hereinafter be abbreviated as A.E. sensor) being attached to the wood.
On the other hand, U.S. Pat. No. 4,895,025 discloses a method in which vibrations induced by wood article destroying insects during their feeding are amplified to an audible level and the thus obtained vibratory sounds are analyzed and compared with other records of known destructive insects on the basis of the fact that vibratory sounds generated during feeding are different depending upon the species of insects, to thereby determine the probable species of insect and its location. This disclosure exemplified a comparison of vibratory behavior by termites to that caused by carpenter ants.
By the way, if no termite detector of the above proposed kinds is set from the beginning, there is no other way for a habitant to know the existence of termites than witnessing a swarm of termites after the destruction has reached an advanced level. And if he or she found them, a lot of swarmings of termites are found in various places in April and May because swarming action of termites occurs all at once in this period. Therefore, the traders of removing termites would have a rush of claims and questions as well as requests for spraying insecticides in this limited period so that it was very difficult for the traders to quickly deal with all such requests.
The above described various termite-detectors have been proposed to deal with the problem just mentioned above. However, the above proposed methods require the examining staff to patrol houses having termite-detectors set to visually check the detectors. The houses with the detector would be scattered in wide ranges, so that the check requires a great deal of time and expense.
In addition, as wooden pieces were used as a material for inducing termites in the conventional arts, such materials are naturally expected to be the same with the wooden building material for a house under test. As a result, even if such materials were used as the detecting samples for inducing termites, it might be considered in a great possible extent that the termites would selectively prefer eating the wooden building materials constituting that house.
Further, as to the aforementioned methods of detecting termites by visually observing the existence of termites in the wood, etc., set on invading passages or by checking, at every time, whether or not wood is damaged by any wood-eating insects using supersonic non-destructive tester, etc.; the present state is that no low-cost sensor for such a detection has been developed yet which allows the system to monitor the house under test around the clock throughout the year.
There is another method in which sounds caused when wood is damaged by termites and transmitted through the wood are measured by using the conventional A.E. sensor and the like. However, in this method, the sounds are picked up from the wood surface through the air with a microphone so that it is impossible to obtain clear sounds. Further, depending upon the situations of the microphone being attached, only particular noises through the air might be picked up so that no one except well-skilled operators can distinguish the wood eating sounds from the noises. Similarly, the aforementioned analyzing means of vibratory waveforms may be considered to require experienced, well-skilled operators.
Moreover, a lot of sensors being placed under floors is hard to find when the inspection is to be carried out.